Rotary nylon line vegetation cutter

ABSTRACT

A rotary cutter head mounted on the end of a handle to power rotate at high speed one or more centrifugally whirled free ends of a reserve of nylon line wound on a spool co-axially pivotally mounted within the head. 
     A co-axially spring biased indexer is subject to inertia applied through the handle while the device is running to effect the feeding of precise increments of line from the spool to the free line ends. The indexer is automatically self-inhibiting when the line ends reach a predetermined optimum length of approximately eight inches and continues to be self-inhibiting until the line ends wear down, in use, to less than a predetermined minimum length of approximately five inches.

This application is a Division of Ser. No. 925,045 filed July 17, 1978,now U.S. Pat. No. 4,185,381.

BACKGROUND OF THE INVENTION

The field of the invention embraces a handle-mounted, hand- manipulatedpower driven rotary head spinning at high speed on a vertical axis withone or more flexible lines, usually made of nylon, radially distendedcentrifugally from said head to very effectively trim vegetationparticularly in lawn edging.

Various expedients have been brought out for facilitating thereplenishing of the working free line end portions as these wear fromuse. These all provide a reserve supply of line wound on one or morespools rotatably confined in the head but normally locked againstrotation. Each expedient offers a different mechanism aiming to make iteasier for the operator to replenish the working cutting line endportions but none of these expedients has as yet proven entirelysatisfactory.

SUMMARY OF THE INVENTION

Included among the objects of this invention are the following:

1. To provide a rotary flexible line vegetation cutting tool in whichthe replenishing of the cutting elements may be accomplished by theoperator without halting the rotation of the tool, and without requiringthe operator to disturb his grip on the handle of his tool or on theengine throttle held in open position in the midst of a job.

2. To provide such a tool in which the only attention required from theoperator to adequately supplement the diminished length of the flexiblefree line ends of the tool is to swing the tool handle downwardly tobump the cutter head, still spinning at top speed, on the lawn or groundor sidewalk directly therebeneath.

3. To provide such a tool in which only increments precisely limited inlength are thus fed to supplement the cutting elements therebypermitting repetition of the bumping cycle to bring the length of theworking line end portions up to par.

4. To provide such a tool which is equipped with an automatic brakingmeans which will inhibit immediate consummation of a bumping cycleinitiated in the face of the fact that the working line end portionsalready have attained their maximum practical working length and willalso abort attempts to initiate any further bumping cycles pending thewearing down of said working line end portions until these are ready tobe further supplemented in length to maintain their efficient cuttingaction.

5. To provide such tool which is very simple to assemble, particularlydue to its housing comprising two identical halves either of which canreplace the other; the reserve line winding spool having an interfacialplane of symmetry permitting it to be optionally assembled with eitherface turned up.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic perspective view illustrating a preferredembodiment of the invention in actual use in trimming vegetation at theedge of a lawn.

FIG. 2 is an enlarged perspective view of the rotary cutter head of theinvention separated from the operating handle and engine shown in FIG.1.

FIG. 3 is an enlarged (full scale) vertical sectional view taken throughthe line emitting windows of the cutter head housing and showing theline spool and feed indexer as they are normally related before startingand during a vegetation cutting operation.

FIG. 4 is a view similar to FIG. 3 excepting for the indexer being hereshown in elevation instead of in section.

FIG. 5 is a view similar to FIG. 4 excepting for its showing the indexerremoved and the arbor and housing shell-hubs broken away to clearlyillustrate the internal structure of the spool of the invention.

FIG. 6 is a vertical sectional view similar to that of FIG. 3 exceptingfor the fact that it illustrates the moment the rotary head of theinvention is subjected by the operator as shown in fIG. 1, to aresounding bump on the lawn or ground therebeneath. This initiates aline feeding step of the invention by utilizing the inertia of theindexer to shift it from its top position in the structure of theinvention (shown in FIGS. 3 and 4) to its lowermost position therein(shown in FIG. 6).

FIGS. 7, 8, 10, and 11 are successive full scale horizontal plandiagrams taken on the line 7--7 of FIG. 4 of the relative positionsassumed by the spool and indexer of the invention as a result of thebumping of the device as shown in FIG. 6.

FIG. 9 is a full scale horizontal bottom plan diagram taken on the line9--9 of FIG. 4 of said spool and indexer and illustrating one of thesteps of a line indexing operation.

FIG. 12 is a diagrammatic perspective view of the indexer of theinvention.

FIG. 13 is a vertical axial cross sectional view of the rotary cutterhead housing of the invention which comprises two identical housinghalves secured in face-to-face abutment with each other, this view beingtaken on line 13--13 of FIG. 14.

FIG. 14 is a horizontal cross sectional view of FIG. 13 taken on theline 14--14 thereof.

FIG. 15 is a side elevational view taken on the line 15--15 of FIG. 13.

FIG. 16 is a diagrammatic perspective view of the reserve nylon linecarrying spool of the invention.

FIG. 17 is a plan view of said spool.

FIG. 18 is a cross sectional view of said spool taken on the line 18--18of FIG. 17.

DETAILED DESCRIPTION OF THE INVENTION

While the rotary line cutter head 15 of the invention shown in FIGS. 2,3, 4, 5 and 6 of the drawings is adapted for reception upon the lowerdrive ends of most of the large size models of handle mounted powerassemblies commonly marketed for nylon line vegetation trimmers, it ispreferably associated with the gasoline engine powered handle assembly16 shown in FIG. 1.

The straight tubular handle 17 encloses a shaft 18 connecting an engine19, mounted on the handles' upper end to a knuckle 20 at its lower endfor making an angular drive connection between the shaft 18 and avertical threaded driving screw 21 which the upper end of the hexagonalarbor 22 of head 15 has a tapped hole 23 to receive.

Referring now to FIGS. 3, 4 and 5, the drive head 15 is seen to includeupper and lower housing halves 30 and 31 which are identical so as to beunited by arbor 22 to form rotatory cutter head housing 32 enclosing aflat cylindrical chamber 33 and presenting hex apertured shallow hubs 34to the main hex body 35 of arbor 22. Upper and lower extremities ofarbor 22 are turned down to penetrate the central apertures of housinghalves 30 and 31 as shown and provided with external threads 36 and 37.

The housing 32 has upper and lower peripherally tapered horizontaloutside walls 38 inwardly from which are molded annular spool bearingtracks 39.

The inside diameter of the housing chamber 33 is formed by the inner oftwo concentric peripheral walls, outer wall 45 and inner wall 46, andthe latter just provides adequate room for free rotation within chamber33 of a vegetation cutting line magazine spool 47.

The outer and inner peripheral walls 45 and 46 of upper and lowerhousing halves abut face-to-face in the housing medial plane and certaindiametrically opposed portions of said halves are partially filled insolid and provided with like opposed inner edge notches 48 which matchto form two line escape windows 49. Vertically aligned closely spaced1/2" roller bearing cups 50 are molded in the partly filled in portionsof walls 45 and 46 to rotatably trap pairs of rollers 51 spaced apartabout one-eighth of an inch and located symmetrically with thelongitudinal diametral axial plane of said line escape windows 49.

Between the opposite areas of outer and inner peripheral walls 45 and 46where the line escape windows 49 are formed, these walls are left quitethin for weight reduction purposes. Plastic material is preferred inmaking housing halves 30 and 31 as well as the spool 47.

The latter element, as can be seen in FIG. 5, is molded so as to besymmetrical about the medial plane at which the housing halves 30 and 31abut. It is of course also freely rotatable co-axially with respect tothe housing 32 within the limits imposed by the controls provided by theinvention.

Being symmetrical about its interfacial axial plane spool 47 willfunction just the same no matter which end is turned up in the assemblyof the invention.

A similar facility in assembling and repairing the invention is servedby the identity of the upper and lower housing halves 30 and 31.

The spool 47 has a thin-walled cylindrical hub 52, the inside bore ofwhich is about three times its axial length and has like outwardlyperipherally beaded flat radial flanges 53 which are extended into closerotational relation with inner housing peripheral walls 46 by very thinradial peripheral spool flanges 54.

It is to be noted that the square cross sectioned annular beads 55 onflanges 54 extend axially outwardly into matching bearing relation withhousing spool positioning tracks 39.

Referring now to both FIGS. 5 and 7, it is noted that spool 47 hasmolded thereon to extend radially inwardly from the bore of cylindricalhub 52, symmetric with the medial horizontal plane of symmetry of spool47, four square edged stops 60, each 50° in length, these stops beinguniformly spaced apart 40° so as to be spaced apart 90° on centers.Filling in the space overlying and underlying the outwardly beadedradial peripheral spool flanges 53 and exactly circumferantiallyoriented with the medial stops 60 in the bore of hub 52, are four upperand four lower radial stops 61.

Non-rotatably slidable vertically on the hex body 35 of arbor 22 withinthe spaces in chamber 33 not occupied by spool 47 is an indexer 62. Thiselement is preferably formed of metal and is designed to be die cast. Itthus comprises a unitary annular metal body 63 having a decreased outerdiameter at its lower end to provide an annular outer shoulder 64 aboutone third of the way from its bottom end. Midway between its oppositeends an internal metal web 65 integrally unites the annular body 63 witha thin walled short hub 66 having a hex shaped aperture 67 slideablyreceiving the hex body 35 of arbor 22 so as to slide freely on saidarbor while being held at all times non-rotatable thereon.

Referring now to FIGS. 4 and 7, it is to be noted that annular indexerbody 63 has four narrow and relatively long lugs 68 formed integral withthe body at its upper end and extending radially externally therefrom at90° intervals. Just above the level of shoulder 64, four short lugs 69are formed integral with body 63 and extend radially therefrom at 90°intervals with each other but 45° out of phase with long lugs 68.

Referring now to FIGS. 3 and 6, it is noted that in assembling therotary head 15, a light coil spring 70 is inserted over the lower hexapertured hub 34, and the indexer 62 is lowered on the arbor 22 andspring 70 as shown in FIG. 3.

Putting together FIG. 3, FIG. 4 and FIG. 7, it will be clear that theassembly shown in these views could not have been effected unless thespool 47 had been turned to place the medial plane spool stops 60 out ofvertical registry with short indexer lugs 69. FIG. 7 shows the requirednon-registry of stops 60 with lugs 69 so that the lugs 69 verticallyby-pass the stops 60 as shown in FIGS. 3, 4 and 6, permitting upper andlower housing halves 30 and 31 to be brought into face-to-face abutmentand the fastening means applied to consummate the assembly.

These means include screwing a polyurethane molded bounce button 71 onthe lower external threads 37 of arbor 22 and screwing a nut 75 on theupper external threads 36 of said arbor.

Wound clockwise on the spool 47 before it is assembled within the rotarycutter head 15 is a doubled length of solid nylon line 76. The bight 77at the inner turn of this doubled length of line is anchored to thespool by threading the two half lengths of the line through a closelyspaced pair of holes 78 provided at a convenient spot in the hub 52 ofthe spool (see FIGS. 3, 4, 5 and 6). After the double line is then woundon the spool, the respective end portions 79 of the line 76 are fedoutwardly through the windows 49 to provide the required vegetationcutting elements when the tool is operated as shown in FIG. 1.

OPERATION

When the rotary cutter head 15 is assembled as above described, it isunited with the engine powered handle assembly 16 by screwing thevertical power output screw 21 into the tapped bore 23 in the upper endof the arbor 22, thereby rotatably suspending the cutter head on saidpowered handle assembly.

To operate the device for cutting vegetation as in trimming the edge ofa lawn (see FIG. 1) it is merely necessary for the operator to put onthe power assembly supporting harness 80, start the engine 19 and revthis up to near top speed while manipulating the tool into engagementwith vegetation to be cut as illustrated in this view.

It is common practice to rotate nylon line cutting heads in excess of6000 rpm. The present invention is designed to follow this practice andto replenish the extending line end portions 79 as they wear downwithout interrupting the rotation of the cutter head. It is alsodesigned to automatically regulate its functions in this respect toprevent end portions 79 exceeding eight inches in length being fed fromthe cutter head 15. These objects are attained by the following mode ofoperation illustrated in FIGS. 3 through 11 reference to which will nowbe made.

FIG. 7 illustrates in a true scale plan diagram, the relative rotationalrelationship between spool 47 and indexer 62 with the vis a visrelationship existing between the spool stops 60 and 61, respectively,and the indexer lugs 69 and 68 respectively, when the indexer 62 isspring biased into its uppermost operation position shown in FIGS. 3 and4.

During the continuance of the situation thus illustrated, no clockwiserotation of spool 47 relative to indexer 62 and thus no feeding of freshline increments from the windows 49 can take place because of the fourshort lugs 69 extending radially into interlocking relation (you mightsay "splined" relation) with the medial plane spool stops 60.

The initial length of the freely extending cutter line end portions 79is determined by the manual rotation of the spool 47 before insertingthe indexer 62 into the head 15 and at the time the free ends of thedouble stranded nylon line are respectively being manually withdrawnfrom spool 47 through line escape windows 49 in the cutter head housing32.

Whatever the starting length of cutter line end portions 79 may be, thecentrifugal forces applied by such line end portions to the doublestrand turns of nylon line 76 wound on spool 47 which is of coursetransmitted to the spool, to which the inner bight 77 of the line isattached, places the spool 47 under a constant clockwise torque. Thistorque is an essential factor in the functioning of the invention, aswill now be described in detail.

FIG. 7 shows this torque in action biasing the medial spool stops 60against the short indexer lugs 69.

The clockwise torque constantly imposed on spool 47 by the centrifugalforce generated in free whirling line end portions 79 is indicated byarrows T in FIGS. 7-11 inclusive.

It is to be further noted that upper spool stops 61 and upper indexerlugs 68 have truly radial side edges whereby rotation of spool 47relative to indexer 62 is interrupted by frictional abutment over wideareas between the four radially long and narrow indexer lugs 68 and theupper four radially long and not-so-narrow spool stops 61 whichsubstantially inhibits vertical transltion of indexer 62 on arbor 22 toset the stage for a bumping operation designed to generate a measuredfeeding of additional line 76 to extend the length of line end portions79. This inhibition varies with the value of the centrifugal force beingcreated by high speed rotation of cutter head 15 and is a function ofthe length, at any existing moment, of the free whirling line endportions 79.

The opposed areas of the four radially short spool stops 60 and the fourradially short index lugs 69 offer a relatively minor frictionalopposition to the translation of indexer 62 from its upper positionshown in FIGS. 3 and 4 to its lower position shown in FIG. 6 when theexisting line end portions 79 are fairly short.

Assuming this to be the case when the initial bumping of the cutter head15 is undertaken, for the purpose of supplementing the length of lineportions 79, we note in FIG. 6 the resulting downward translation ofindexer 62 lowering lugs 69 out of horizontal alignment with medialspool stops 60 thus freeing the spool for clockwise rotation in responseto the torque T while simultaneously shifting the four indexer upperlong lugs 68 downward into a frictional sliding position resting on theupper radial peripherally beaded spool flange 53 and in horizontalalignment with the four upper spool stops 61 whereby the clockwisetorque constantly being applied to spool 47 spins this to whip the fourupper spool stops 61 into snug frictional engagement with the four longindexer lugs 68 as shown in FIG. 10.

An intermediate step in this 66° line-increment-feedingclockwise-turning movement of the spool 47 is shown in plan in FIG. 8and in bottom plan in FIG. 9.

Assuming the reserve body of line 76 wound on spool 47 has an OD of 3",line increments 1.73" in length are fed from head 15 to each of the lineend portions 79 in the bumping operation just described.

An important characteristic of the invention resides in the fact thatwhen the increments, just fed to supplement the length of line endportions 79, extends these as much as eight inches from the cutter head15, the centrifugally produced torque T being at that moment applied tospool 47 locks the indexer 62 against axial translation by inertiaforces set up by another attempted manual ground bumping operation. Thisfact inhibits an operator from mistakenly feeding excessive amounts ofline 76 from head 15 which would require line end portions 79 to bemanually trimmed in order for head 15 to function satisfactorily. Aneconomical use of line 76 is thus assured without special skill beingrequired by the operator.

The head 15 is designed to remain thus locked, as shown in FIG. 10,against further line increment feeding, until said portions 79 have beenworn down by use to lengths of approximately five inches or less.

When the latter circumstance has occurred, the resulting reduction inthe torque T applied to spool 47 releases the frictional grip of thespool on indexer 62 allowing spring 70 to return the indexer to itsuppermost position shown in FIGS. 3 and 4 which allows spool 47 to turnclockwise to its position shown in FIG. 7 thus completing a cycle of 90°and, incidental thereto, feeding supplemental line increments of 0.83"in length to the line end portions 79.

These split phase line increment feeding functions of the rotary linevegetation cutter head 15 must be understood as normally occurringentirely during the unremitting turning of said head and do not requiremore than a few seconds spent in the bumping function to restore lineend portions 79 to proper operating lengths. In fact, the holding of thetool in the hands while performing a vegetation trimming job maycontinue unchanged while bumping the rotating rotary head 15 inrestoring, to fully operative lengths, the line end portions 79.

Whereas, the control of the indexer 62 may be effectively accomplishedby a succession of bumping cycles described above, an alternate mode ofoperation for achieving the same end is available by employing arelatively light coiled spring 70 which allows the desired translationof the indexer on the arbor 22 to be produced by merely briskly shakingthe handle assembly 16 without contacting the ground in any way with therotary head 15. Use of the term "bumping" in the claims therefore is tobe broadly construed to cover not only this preferred mode of operationof the invention but any equivalent mode of applying inertia to theindexer 62 as by simply shaking the device while it is running and beingwholely supported in the operator's hands.

While the rotary cutting head 15 is shown and described herein asrotating counter clockwise and the reserve line carrying spool 47 isshown and described as rotating clockwise with reference to the head 15when functioning to supplement the length of line free end cuttingportions 79, yet the unique design of the invention adapts it to be usedin association with various motor or engine powered assemblies 16 someof which provide right hand threads on the head supporting and rotatingscrew 21 while others provide said screw with left hand threads. Arbors22 are thus provided optionally with right or left hand internal threadsin the tapped hole 23 in its upper end.

The head 15 will of course turn clockwise when driven by a right handthreaded drive screw 21 and counter clockwise when driven by a left handthreaded screw 21. The connection of the head 15 with the screw 21 willthereby always be firmed up by the drive torque transmitted through thescrew.

The external threads 36 and 37 on the upper and lower ends of arbor 22are preferably right hand threads regardless of the direction head 15rotates.

It is immaterial which direction the spool 47 rotates relative to thehead 15 because in any event, the reserve line wound on the spool isalways being pulled outwardly therefrom centrifugally with each feedingcycle. This feeding is assured by the fact that no matter how thedoubled reserve line is wound upon the spool with the end portions 79extending out through the housing windows 49, the centrifugal forcegenerated in said free end portions of cutting line will turn the spoolin whatever direction the line is wound. Due to the interfacial symmetryinherent in the design of spool 47 and the circumferential symmetry ofthe stops 60 and 61 in said spool, the latter may have the doubledreserve line 76 wound in either direction tangentially from its bight 77and then the spool can be mounted in the head 15 with either end up,while withdrawing the free ends 79 through the opposed window 49, andthe invention will operate exactly the same as described herein.

We claim:
 1. In a flexible line whirling vegetation cutting hand tool, arotary head for which is provided to be supported by and manipulated onthe lower end of a relatively long handle equipped with power means forrapidly spinning said head on a vertical axis, the improvementcomprising the following combination of elements;an annular,cylindrical, double radially flanged spool providing an externalperipheral storage space for winding a reserve supply of flexiblecutting line thereon, said spool having a relatively large diameter boreprovided with suitable circumferentially equally spaced stops; a rotaryhead including a housing providing a cylindrical chamber freelyrotatably confining said spool and having at least one peripheral windowfor the withdrawal of a free end portion of said line from said spoolfor use in vegetation cutting, the centrifugal force thus generated insaid free line portion tending to powerfully unwind said reserve line byrotating said spool relative to said housing; indexing means springbiased to translate said means axially on said housing into a firstposition thereon for locking said spool against such rotation, saidindexing means being responsive to a vertical upward shock applicable tosaid rotary head, as by swinging downwardly the handle of the powerassembly on which said head is rotating at its normal speed, until saidhead strikes the ground while so rotating, to produce a reversetranslation of said indexing means axially to a second position whichfrees said spool, tentatively permitting it to rotate through apredetermined angle to facilitate withdrawal of a corresponding amountof reserve line from the spool and releasing it through said window tosupplement the pre-existing length of said free line end portion, andthereupon automatically concluding said bumping cycle by resuming itsinitial vertical spool locking position; and a braking means associatedwith said indexing means which is automatically responsive to anexcessive centrifugal force being currently generated by a supplementedlength of said free cutting line end portion, to inhibit the immediateconsummation of a consecutively additional bumping cycle.
 2. Acombination as recited in claim 1 whereinsaid braking means neverthelesspermits an immediate partial performance of said additional bumpingcycle in feeding a substantial line supplement to said free line endportion and then braking said indexing means to indefinitely restrain itfrom returning to its initial position, said return automaticallyoccurring only when said centrifugal force reduces due to use of thedevice thereby relaxing said braking means.
 3. A combination as recitedin claim 2 whereinthe relaxing of said braking means causes saidindexing means, in returning to its initial position, to unlock and thenrelock said spool, said spool in the interim feeding a reserve linesupplement to augment the length of said line free end portion.
 4. In aflexible line whirling vegetation cutting hand tool, a rotary head forwhich is provided to be supported by and manipulated on the lower end ofa relatively long handle equipped with power means for rapidly spinningsaid head on a vertical axis, the improvement comprising the followingcombination of elements:an annular, cylindrical, double radially flangedspool providing an external peripheral storage space for winding areserve supply of flexible cutting line thereon, said spool hving arelatively large diameter bore provided with suitable circumferentiallyequally spaced stops; a rotary head including a housing providing acylindrical chamber freely rotatably confining said spool and having atleast one peripheral window for the withdrawal of a free end portion ofsaid line from said spool for use in vegetation cutting, the centrifugalforce thus generated in said free line portion tending to powerfullyunwind said reserve line by rotating said spool relative to saidhousing; indexing means spring biased to translate said means axially onsaid housing into a first position thereon for locking said spoolagainst such rotation, said indexing means being responsive to avertical upward shock applicable to said rotary head, as by swingingdownwardly the handle of the power assembly on which said head isrotating at its normal speed, until said head strikes the ground whileso rotating, to produce a reverse translation of said indexing meansaxially to a second position which frees said spool, tentativelypermitting it to rotate through a predetermined angle to facilitatewithdrawal of a corresponding amount of reserve line from the spool andreleasing it through said window to supplement the pre-existing lengthof said free line end portion, and thereupon automatically concludingsaid bumping cycle by resuming its initial vertical spool lockingposition; a hexagonal arbor means extending axially through said housingchamber, said means assembling and transmitting power to said rotaryhead; said indexing means including an annular indexer slideably fittingand being translatable axially on said arbor means within said spoolbore and being spring biased normally into a given position in saidbore, said indexer being adapted to be inertia shifted by a bumpingcycle to a different position in said spool bore; said indexing meansalso including stop and lug means provided respectively on said spooland on said indexer and interacting normally to lock said spool againstrotation relative to said housing but responding to said bump to freesaid spool to permit it to yield to said centrifugal force and feed apre-determined length of reserve line from said spool to supplement thelength of said free end line portion; and wherein certain of said stopmeans are brought into such rotary frictional engagement with certain ofsaid lug means by said rotation of said spool as to constitute a brakingmeans tentatively preventing a repetition of said bumping cycle until anexcessive degree of centrifugal force in said free line portion issubstantially reduced by use, thereby freeing said indexer from saidbraking means, and returning said indexer and spool to their respectivecharacteristic relative starting positions.
 5. A combination as recitedin claim 4 whereina primary line supplement feeding rotation ofapproximately 66° is imparted to said spool between the unlocking ofsaid spool by said bump and the tentative relocking of the spool by saidexcessive line torque, and a secondary line supplement feeding rotationof approximately 24° is imparted automatically to said spool when it isreleased from said indexer by said diminishing torque applied to saidspool through said free line end portion, thereby concluding anaggregate 90° of line feeding rotations by said spool during a singlebumping cycle.
 6. A combination as recited in claim 4 whereinsaid spoolhas an interfacial plane of symmetry containing at least three primaryshallow internal stops of equal length and circumferentially equallyspaced apart; and wherein at least one radial flange of said spool,turned upwardly in said chamber, is provided with secondary shallowupper level stops extending upwardly from said radial spool flange incircumferential symmetry with said primary internal stops; and whereinsaid indexer includes a substantial annular body closely fitting withinthe bore of said spool and co-axially translatable on said arbor meansand being spring biased upwardly into said given position and inertiashiftable downward in opposition to said bias by a bumping cycle intosaid different position; and wherein said indexer body has short lowerlevel lugs extending radially therefrom into close proximity with thebore of said spool and interlockingly interspersed circumferentiallywith said lower level spool stops when said indexer is in its upperposition; and wherein the upper extremity of said indexer body isprovided with relatively long radial lugs equal in number with saidsecondary spool stops and equally spaced circumferentially on theindexer and limiting downward translation of said indexer by coming torest on top of said upper spool flange, said long upper lugs alsoreceiving torque pressures from said secondary spool stops generated byrotation of said free line end portion, said torque producing brakingpressures inhibiting the return upward of the indexer to its initialposition until a substantial decrease in said torque occurs.
 7. Acombination as recited in claim 6 whereinthere are four interfacialspool stops and four upper spool stops which are arranged on said spoolcircumferentially equally spaced on centers with the stops at said twolevels being in symmetrical vertical alignment; and wherein there arefour long narrow, shallow uppr level lugs extending radially from saidindexer body which are equally spaced circumferentially, and four shortnarrow shallow lugs extending radially at a lower level from saidindexer body the latter four lugs being equally spaced circumferentiallywith each other but being 45° out of phase rotationally with said upperlevel lugs; said lower lugs circumferentially interlocking with saidlower stops when said indexer is in its upper position and disengagingsaid lower stops when said indexer is translated axially into its lowerposition. said upper lugs circumferentially interlocking with said upperstops when said indexer is in its lower position and disengaging saidupper stops when said indexer is in its upper position.
 8. In a flexibleline whirling vegetation cutting hand tool, a rotary head for which isprovided to be supported on and manipulated by the lower end of arelatively long handle equipped with power means for rapidly spinningsaid head on a vertical axis, the improvement comprising the followingsubcombination of elements:a pair of like hollow circular housing halvesabutting in face-to-face relation to provide a cylindrical housing forsaid rotary head, said housing halves having co-axially aperturesincluding polygonal internal wrench configurations; a polygonal arboropposite end portions of which snuggly fit into said wrenchconfigurations to prevent relative rotation between said housing halves,said arbor having threaded means of reduced diameter extending axiallyat its opposite ends through said co-axial apertures to receive nutmeans for snugly assembling said housing halves on said arbor; drivemeans connecting the upper end of said arbor to said power means; theabutting edges of said housing halves having notch means which saidarbor means hold in opposed matched relation to form a pair ofdiametrically opposite peripheral cutting line escape windows in saidhousing; said housing providing a cylindrical line reserve spoolconfining chamber with which chamber said windows communicate; a reserveline would spool rotatably confined within said chamber and held againstshifting axially therein by annular track means molded in said housinghalves; said spool having a thin walled hub, the bore of which has asubstantial diameter; an inertia manipulated annular indexer slideablybut nonrotatably spring biased axially on said arbor means; and stop andlug escapement means on said indexer and said spool governing rotationof said spool caused by the centrifugal force generated in said free endportions of said cutting line.